Track idler wheel

ABSTRACT

A method and apparatus in the form of a heavy-duty track idler wheel comprising two formed discs that have integrally formed outer rims and inner bosses concentrically abutting each other and joined by circumscribing weld joints.

United States Patent [191 Clasper et a1.

[ 51 Nov. 13, 1973 1 TRACK IDLER WHEEL [75] Inventors: Thomas Clasper,Belmont; Wilfred H. Hutton, Ryton-on-Tyne, both of England; Orville E.Kessinger, Jr., Mackinaw, 111.; Victor Randour, Aurora, 111.; Fred E.Simpson,

Oswego, Ill.

[73] Assignee: Caterpillar Tractor Co., Peoria, 111.

[22] Filed: Oct. 22,1971

21 Appl. No.: 191,597

[52] US. Cl 305/21, 74/230.3, 301/63 DD,

305/56 [51] Int. Cl B60b 3/08 [58] Field of Search 301/63 DD; 305/21,

[56] References Cited UNITED STATES PATENTS 306,070 10/1884 Ferguson301/63 DD 900,700 10/1908 Bole 74/2303 2,926,969 3/1960 Ashley 305/323,490,285 1/1970 Schaeffler.... 74/2305 2,284,821 6/1942 Heaslet 305/32FOREIGN PATENTS OR APPLICATIONS 225,034 10/1959 Australia 301/63 DDPrimary Examiner-Richard J. Johnson Assistant ExaminerReinhard EisenzopfI Att0rneyFryer, Tjensvole, Feix, Phillips & Lempio [57] ABSTRACT Amethod and apparatus in the form of a heavy-duty track idler wheelcomprising two formed discs that have integrally formed outer rims andinner bosses concentrically abutting each other and joined bycircumscribing weld joints.

4 Claims, 3 Drawing Figures mum-m 1 PRIOR ART 4 TEL TRACK IDLER WHEELBACKGROUND OF THE INVENTION Earthmoving machines, and in particularcrawler tractors, are subject to some of the most severe environmentaloperating conditions experienced by any mechanized equipment. Crawlertractors commonly pioneer new roads and prepare virgin soil imbeddedwith rock and other debris that severely punish the track and otherground supporting components. The idler wheels, normally disposed at theforward end of each ground-engaging track chain that is used formotivating and steering such tractors, are particularly exposed to highrates of wear and damage due to the fact that they are subject to andabsorb much of the initial shock loads generated when projecting rocks,tree stumps, etc., are encountered. Also contributing to high rates ofwear and damage is the high horsepower employed with these machines.Very high quality undercarriage components are required to ensuredesired long service life. To provide durable track idler wheels,manufacturers of earthmoving equipment have often provided single piece,cast steel idlers and/or have fabricated such idlers in numerous anddiverse patterns in an effort to obtain increased strength for thiscritical track support member. In spite of these efforts, theseconventional idler wheels occasionally fail when subjected to the severeservice conditions aforementioned.

SUMMARY AND OBJECTS OF THE INVENTION This invention relates to a trackidler wheel especially made for heavy-duty tractor applications havingtwo formed metallic discs disposed in abutting concentric relationshipand joined by circumscribing weld joints in such a manner as to minimizestresses inherent in the composite disc idler wheel structure.

A primary object of this invention is to use two basically symmetrical,formed, metallic discs in an abutting, concentric, and coactingrelationship to produce a more durable track idler wheel that is stilleconomic to produce. I

Another object of this invention is toemploy formed or cast metallicdiscs in cooperating relationship as a track idler wheel so that asshockloads are experienced, internal stresses will be uniformlydispersed by the idler wheel.

Another object of this invention is to employ pairs of formed metallicdiscs in such a manner that they may be economically and expedientlyassembled as component parts of a track idler wheel with a minimum ofmanual labor.

Another object of this invention is to provide a composite wheel made upby welding a pair of discs together having a hollow space therebetweenso as to take advantage of the superior strength properties of box beamconstruction.

Another object of this invention is to provide a composite wheel havingweld joints at locations where induced loads are at a minimum.

Yet another object of this invention is to provide a composite wheelhaving weld joints located so as to facilitate assembly and reduce laborcosts.

Another object of this invention is to provide a composite wheel suchforged wheel discs provide strength at locations where induced loads areat a maximum.

made up of forged wheel discs wherein BRIEF DESCRIPTION OF THE DRAWINGSIn the drawings:

FIG. 1 is a view in partial section of a conventional idler and a trackchain showing how in constructing prior art idlers, two generallysymmetrical metal discs are welded to a rim andinner boss to form theidler wheel;

FIG. 2 is a sectional view in perspective of the idler wheel of thisinvention comprising two symmetrical discs connected by circumscribingweld joints; and

FIG. 3'shows a modified form of the idler wheel of this inventionwherein a steel tube is employed centrally within the wheel to' couplethe disc members and to serve as a bearing hub structure.

DETAILED DESCRIPTION As ,shown in FIG. 1, a track idler wheel generallyshown at 10 and employed in the crawler chain of earthmoving tractorsnormally comprises a cylindrical rim section 12 of a predetermined widthto coincide with laterally spaced, cooperating links 14 of aconventionalarticulated joined track chain shown generally at 16. Relativelyrotatingpins and bushings l8 and 20 pivotally couple the ends of thelinks to form an endless track chain which is supported onground-engaging track shoes 22 that are secured thereby by bolts 24. Acentral, diametrically enlarged portion 26 of rim section 12 is normallyemployed intermediate two axially spaced load or rail supporting rimportions 28 so that radially extending side surfaces 30 might contactand maintain track alignment through the inner contiguous link surfaces32.' v v To minimize weight of the idler, laterally spaced, disc-shapedmembers 34 are employed to circumferentially support the idler rim 12upon a central boss or hub 36 that, in turn, is rotatably mountedthrough bearings 38 on a support shaft 40. The idler may be adapted to arecoil mechanism (not shown) for horizontal and longitudinalreciprocation upon slide bearings 42, in order to cushion shock loads asthey are encountered.

As shown in FIG. 1 the idler in the area of the juncture of supportingside discs 34 and rim portions 28 exhibits abrupt changes in contourproximate to the outer circumferential weld joints 44. This allowsconcentrated loads generated by encountering groundimbedded obstructionsto be detrimentally applied to the idler components through themechanism of a stress-riser relationship. The consequence of this actionis that the weld joints begin to crack, propagating cirgrally formedthereon one-half of outer rim 12 and one-half of inner boss or hubsection 36'. Large radii form broad transitional junctures 50,52immediately inward of the high-impact area of each load-bearing rim 28and about the hub section of 54,56 to minimize high stressconcentrations. Integral rims and hubs with smooth transition areas arereadily adaptable to both conventional and rotary forging techniques. Byplacing a disc upon a rotatable table (not shown) with a recessconforming to the desired shape of the idler, forming tools are broughtinto rotating engagement with the metal disc, and upon application ofsufficient force, the material is worked into the required areas toprovide the large radii and specific shape of the desired rim and hubportions.

The method of manufacture of such forged idlers will now be describedwith particularity. As is conventional with the production of forgedrailroad car wheels the steps of manufacture of the discs are asfollows: (1) heating a metal billet or ingot to forging temperature; (2)forging the ingot into a solid disc; (3) forging the disc into a basicwheel shape with inner bosses and an outer rim; (4) piercing a holethrough the basic wheel shape; (5) roll forging the outer rim profile tothe required dimensions; and, (6) dishing (press forging) the completeforging in a press. Having thus described the conventional steps, themethod of the instant invention further comprises the steps of (7)repeating steps 1-6 to produce a second wheel disc; (8) placing the twodiscs in side-by-side abutting relationship wherein the rims and bossesof the respective discs are in contact and (9) welding the two discstogether at their points of contact.

In the alternative, steps l 6 can be replaced by the step of castingrather than forging the wheel disc. Such casting step would beaccomplished as is conventional in the art.

The overall diameter of such track idler wheels is normally small enoughthat they can also be manufactured on conventional, press-type forges.Specifically, forging beneficially works the material grain structureinto flow patterns that provide additional strength to transition areas50,52,54,56 as they attain their desired shapes. Homogenity of dimensionof the idler wheel discs is desired because the abutting surfaces of thecoacting parts must align concentrically so that an outer circumscribingweld joint 58 and an inner annular weld joint 60 can join the two discs34 in an effective manner.

The concentric alignment of the coacting wheel discs or sections may beassured by initially machining bore 62, which is then mounted securelyon a supporting pilot shaft (not shown) for subsequent machiningoperations of the remaining outer surfaces and edges of the rim andwheel. Rather than using the welding techniques described above, the twoidler wheel hubs and rims could be inertia friction welded by rotatingone disc relative to the other disc at a predetermined speed,

and then bringing the two members together under substantial force andallowing the resultant wheel to come to a stop. Inertia weldingequipment disclosed in the Assignees U.S. Pat. No. 3,273,233, may beused to accomplish such welds.

Limited finish machining of the wheel often would be required to shapethe external surfaces of the hub to adapt them to support bearingassemblies analogous to 38 in FIG. 1. In this case, such additionalmachining step would be performed subsequent to joining the two discs.

FIG. 3 shows a partial cross section view of a modified idlerwheelassembly 10" wherein two symmetrically formed discs 34" are flaredout so that substantially larger, broader junctures 52" are employedintermediate the circular sidewalls, rim 12", and hub section 36". Whensuch metal discs are placed upon rotatable forging tables or dies 64,suitable apertures 66 are normally provided in the discs to receivepilot drive pins 68 so as to maintain the radial position of the discsand to provide a drive force while they are being worked. With thesubject idler, an extra tool would be employed to work the outerperiphery of the rim sections 12" so that metal displaced during sizingof the load bearing rim sections can be transferred and formed intorelatively thin, outwardly extending radial flanges 70. These are theguide surfaces which are required to contact and maintain track chainalignment.

Additional strength is afforded the hub portions 36" of the FIG. 3embodiment by inserting and welding a section of steel tubing 72 intocentral disc apertures 48". Using a tube of metal such as steel in thehub area in combination with the heavier sections of the discs at theirinner bores not only afi'ords substantially higher beam strength toresist internal loading of the idler, but also provides the opportunityto manufacture weld joints 74 by applying the weld to the outer diameterof tube 72. This is often more convenient and economical than weldingjoint of FIG. 2, for example, since it is more difficult to make aninside weld within a tube than an outside weld as described.

With the subject embodiment, additional steps of inserting tube 72 intoapertures 48" and applying two welds 74 to the juncture between thediscs and the tube are required.

It should be further noted that chamfers 76 and 78 in the embodiment ofFIG. 2 and 76" in the embodiment of FIG. 3 may be formed in the discduring the manufacture of the discs to facilitate welding.

It is to be understood that the foregoing description is merelyillustrative of preferred embodiments of the invention and that thescope of the invention is not to be limited thereto, but is to bedetermined by the scope of the appended claims.

What is claimed is:

1. An idler wheel comprising a pair of generally symmetrical circularwheel discs of integral one-piece construction, each wheel disc havingan enlarged axially directed circular outer rim and an axially directedcircular inner boss, said rim and boss being joined by a generallyradially directed wall, said wheel discs being in side-by-side abuttingrelationship wherein the respective rims and bosses of each wheel discare in contacting relation over a circular line of contact forming ajuncture between the wheel discs, said bosses defining a generallycentrally located cylindrical bore through the wheel, means joining saidwheel discs together comprising a circumscribing weld peripherallyaround the line of contact forming the juncture between the rims at theradially outermost part of the wheel and the bosses at the radiallyinnermost part of the wheel within the cylindrical bore, so as to form acomposite idler wheel having a hollow space therein, and wherein eachrim comprises a load bearing shoulder portion directed axially away fromthe other wheel disc of the pair and a central flange portion of greaterdiameter than the mize stress concentrations.

3. The invention of claim 2 wherein the large radii transition juncturesare located radially inward of the shoulder portion.

4. The invention of claim 2 wherein the discs are further formed so asto include large radii transition junctures at the juncture of the bossto the wall.

1. An idler wheel comprising a pair of generally symmetrical circularwheel discs of integral one-piece construction, each wheel disc havingan enlarged axially directed circular outer rim and an axially directedcircular inner boss, said rim and boss being joined by a generallyradially directed wall, said wheel discs being in side-by-side abuttingrelationship wherein the respective rims and bosses of each wheel discare in contacting relation over a circular line of contact forming ajuncture between the wheel discs, said bosses defining a generallycentrally located cylindrical bore through the wheel, means joining saidwheel discs together comprising a circumscribing weld peripherallyaround the line of contact forming the juncture between the rims at theradially outermost part of the wheel and the bosses at the radiallyinnermost part of the wheel within the cylindrical bore, so as to form acomposite idler wheel having a hollow space therein, and wherein eachrim comprises a load bearing shoulder portion directed axially away fromthe other wheel disc of the pair and a central flange portion of greaterdiameter than the shoulder portion, said central flange portion defininga generally radially directed side surface portion and a generallyaxially directed portion, said side surface portions adapted formaintaining track alignment.
 2. The invention of claim 1 wherein thediscs are formed so as to include large radii transition junctures atthe juncture of the rim to the wall at a location inward of the loadbearing shoulder portion so as to minimize stress concentrations.
 3. Theinvention of claim 2 wherein the large radii transition junctures arelocated radially inward of the shoulder portion.
 4. The invention ofclaim 2 wherein the discs are further formed so as to include largeradii transition junctures at the juncture of the boss to the wall.